Used tires include materials that, if successfully recycled, may be used for a wide variety of industrial uses. However, due to the difficulty in recycling these materials, millions of tires every-year are worn out and accumulated. Such used tires if burned cause air pollution. Burying tires leads to landfill contamination. Further, since waste tires are bulky, they take up a significant amount of space, even if compacted. Stockpiling of tires and special treatment of tires in landfills further requires a much more costly operation than disposal of other types of solid waste, such that landfill operators tend to exact a higher charge for disposal of such materials. Such high costs lead to indiscriminate dumping which causes many environmental hazards, from mosquito breeding grounds in the pooling of water within tires to fire hazards since burning tires are very difficult to extinguish as well as a significant eyesore on the landscape.
Tire recapping has declined due to the tendency of more people to prefer steel belted radials. Such tires are more difficult to recap so that most of these tires end up in landfills. Such tires are also more difficult to further process for recycling. Retreading of tires is also not commonly performed on waste tires since the processes are not universally useful on all tires, are still costly and are difficult for steel belted radials. While there have been other uses for used tires, such as for artificial underwater reefs, crash barriers, road building, playground surfaces and the like, these uses still do not satisfactorily use the large number of waste tires generated each year.
Tire pyrolysis processes are known in which tires are destructively heated in the absence of oxygen to produce useful end products such as oils, gases and carbon black. However, there is difficulty in achieving commercial viability for such processes since the costs of recovering the end products is more costly than the costs associated with deriving these materials directly from petroleum. Further, the quality of the carbon black achieved is typically not commercially acceptable. Further, processing problems arise in that pyrolysis results in the generation of fumes that are flammable in the presence of oxygen. Also, under certain conditions, undesired gaseous byproducts may be formed. It has also been difficult to make beneficial use of the end products of pyrolysis for several reasons, including low yields (which render some prior art processes not economically feasible), and poor quality end products (which limits the market for re-sale of such end products). This is particularly true for carbon black end products from pyrolysis which tend to have high levels of volatiles.
Accordingly, there is a need in the art for a tire pyrolysis process which produces marketable carbon and fuel products, and which is economical and commercially viable.